Incremental Treadmill Exercise Test Research Articles

Heart size estimated by echocardiography correlates with maximal oxygen uptake.

Maximum oxygen uptake also appears to correlate to athletic performance in horses. In the Thoroughbred industry, there has long been an empirical theory that heart size is related to athletic performance, despite a lack of scientific evidence supporting this assertion. To investigate the relationship between peak oxygen consumption (VO2max) and cardiac size measured by echocardiography, guided M-mode and 2-dimensional echocardiography were performed in 17 conditioned Thoroughbreds with a range of VO2max from 126 to 217 ml/min/kg STPD (mean +/- s.d. 158 +/- 28 m/min/kg). Horses were age 2-10 years and weighed 430-510 kg. Echocardiography was performed using a Vingmed System V echocardiograph with a 2.25 MHz phased array ultrasound transducer. All images were obtained from the right hemithorax using a short axis view of the left ventricle (LV) at the level of the chordae tendinae. All horses were free from significant regurgitation at the aortic or mitral valves. Maximal oxygen uptake was measured during a standardised incremental treadmill exercise test to fatigue. Maximal oxygen uptake was correlated significantly with LVIDd (r = 0.71; P = 0.001), MWT (r = 0.72; P = 0.001), LV mass (r = 0.78; P = 0.0002) and LV short-axis area (r = 0.69; P = 0.003). When indices of heart size were indexed to bodyweight, the correlation between VO2max and indices of heart size were LVIDd (r = 0.57; P = 0.01), MWT (r = 0.44; P = 0.07), LV mass (r = 0.78; P = 0.0002) and LV short-axis area (r = 0.69; P = 0.003). The current study suggests there is a strong relationship between VO2max and measurements of left ventricular size in Thoroughbred horses when individuals with a range of VO2max are compared.

Ventilatory efficiency and rate of perceived exertion in obese and non-obese children performing standardized exercise.

Sixty children, in the age span 6-17 years originally divided into two groups, matched by age, sex and height--30 obese subjects [15 girls/15 boys; body mass index (BMI) = 27.4 +/- 4.5 m kg-2; ideal body weight (IBW) range = 122-185%] and 30 controls (BMI = 18.8 +/- 2.7 m kg-2) performed incremental treadmill exercise test. Perceived exertion was assessed by means of Category-Ratio Borg scale. The duration of the exercise for the children in the obesity group was significantly shorter than controls (P = 0.010) but obese children have greater absolute values for oxygen uptake (VO2peak ml min-1 = 1907 +/- 671 versus 1495 +/- 562; P = 0.013) and ventilatory variables (VE, VT), which adjusted for body mass decrease significantly (VO2/kg ml min-1 kg-1 = 29.2 +/- 3.8 versus 33.6 +/- 3.5; P < 0.001). Among the various methods for 'normalizing' absolute values of VO2peak for body size, dividing it by body surface area (BSA) yielded the best results (VO2/BSA ml min-1 m-2 = 43.5 +/- 4.6 versus 44.7 +/- 5.6; P = 0.335). The ventilatory efficiency determined either as a slope of VE versus VCO2 or as a simple ratio at anaerobic threshold did not differ between obese and non-obese children in the incremental and recovery periods of exercise. There was a negative correlation of VE/VCO2 slope with age and anthropometric parameters. Obese children rated perceived exertion significantly higher than controls despite the standard workload (Borg score = 6.2 +/- 1.2 versus 5.2 +/- 1.1; P = 0.001). In conclusion, the absolute metabolic cost of exercise is higher in the obesity group compared with the control subjects. Both groups have similar ventilatory efficiency but an increased awareness of fatigue that furthermore limits their physical capacity.

Role of lung inflammatory mediators as a cause of exercise-induced arterial hypoxemia in young athletes.

We examined whether lung inflammatory mediators are increased during exercise and whether pharmacological blockade can prevent exercise-induced arterial hypoxemia (EIAH) in young athletes. Seventeen healthy athletes (9 men, 8 women; age 23 +/- 3 yr) with varying degrees of EIAH completed maximal incremental treadmill exercise tests after administration of fexofenadine, zileuton, and nedocromil sodium or placebo in a randomized double-blind crossover study. Lung function, arterial blood gases, and inflammatory metabolites in plasma, urine, and induced sputum were assessed. Drug administration did not improve EIAH or gas exchange during exercise. At maximal exercise, oxygen saturation fell to 91.4 +/- 2.6% (drug trial) and 91.9 +/- 2.1% (placebo trial) and alveolar-arterial oxygen difference widened to 28.1 +/- 6.3 Torr (drug trial) and 29.3 +/- 5.7 Torr (placebo trial). Oxygen consumption, ventilation, and other exercise variables were similarly unaffected by drug treatment. Although plasma histamine increased with exercise, values did not differ between trials, and urinary leukotriene E(4) and 11beta-prostaglandin F(2alpha) levels were unchanged after exercise. Postexercise sputum revealed no significant changes in markers of inflammation. These results demonstrate that EIAH in young athletes is not attenuated with acute administration of drugs targeting histamine and bioactive lipids. We conclude that airway inflammation is of insufficient magnitude to cause impairments in gas exchange and does not appear to be linked to EIAH in healthy young athletes.

An Evaluation of Two Approaches to Exercise Conditioning in Pulmonary Rehabilitation

To compare the effectiveness of two forms of exercise training in pulmonary rehabilitation. A prospective, randomized, unblinded, 8-week trial. A hospital-based outpatient pulmonary rehabilitation program. Forty patients (20 patients in each group) with COPD who were referred for pulmonary rehabilitation. We compared the short-term effectiveness of a high-intensity, lower-extremity endurance program with a low-intensity, multicomponent calisthenics program for the rehabilitation of patients with COPD. The high-intensity group trained predominately on the stationary bicycle and treadmill, with a goal of exercising at > or = 80% of maximal level determined from incremental testing for 30 min per session. The low-intensity group performed predominately classroom exercises for approximately 30 min per session. For both groups, twice-weekly sessions were held for 8 weeks. The primary outcome measure was health status, measured using the Chronic Respiratory Disease Questionnaire. Other outcomes included peak oxygen consumption on incremental treadmill exercise testing, exertional dyspnea, treadmill endurance time, the number of sit-to-stand repetitions and arm lifts in 1 min, overall dyspnea, and questionnaire-rated functional status. Both groups showed significant postrehabilitation improvement in exercise variables, exertional and overall dyspnea, functional performance, and health status. Patients in the high-intensity group showed greater increases in treadmill endurance and greater reductions in exertional dyspnea, whereas those in the low-intensity group showed greater increases in arm-endurance testing. Both groups had similar improvements in overall dyspnea, functional performance, and health status. Despite differences in exercise performance, both high-intensity, lower-extremity endurance training and low-intensity calisthenics led to similar short-term improvements in questionnaire-rated dyspnea, functional performance, and health status.

Effect of topical anesthesia of the laryngeal mucosa on upper airway mechanics in exercising horses.

To determine the effect of desensitization of the laryngeal mucosal mechanoreceptors on upper airway mechanics in exercising horses. 6 Standardbreds. In study 1, videoendoscopic examinations were performed while horses ran on a treadmill with and without topical anesthesia of the laryngeal mucosa. In study 2, peak tracheal and nasopharyngeal pressures and airflows were obtained from horses during incremental treadmill exercise tests, with and without topical anesthesia of the laryngeal mucosa. A nasal occlusion test was performed on each horse while standing during an endoscopic examination for both trials. In study 1, horses had nasopharyngeal collapse while running on the treadmill when the laryngeal mucosa was anesthetized. In study 2, inspiratory upper airway and nasopharyngeal impedance were significantly higher, and peak tracheal inspiratory pressure, respiratory frequency, and minute ventilation were significantly lower in horses when the laryngeal mucosa was anesthetized, compared with values obtained when horses exercised without topical anesthesia. Peak inspiratory and expiratory airflows were lower in horses when the laryngeal mucosa was anesthetized, although differences did not quite reach significance (P = 0.06 and 0.09, respectively). During a nasal occlusion test, horses had episodes of nasopharyngeal collapse and dorsal displacement of the soft palate when the laryngeal mucosa was anesthetized. Upper airway function was normal in these horses without laryngeal mucosal anesthesia. Receptors within the laryngeal mucosa may be important in maintaining upper airway patency in exercising horses.

NA+-H+-EXCHANGER ACTIVITY IN HUMAN LYMPHOCYTES AFTER ANAEROBIC EXERCISE

The Na+-H+-exchanger is an essential part in cellular pH-regulation (pHi) and volume control. The objective of the present study was to investigate its activity after acute and chronic acid loading. In part I of the study 16 healthy volunteers performed an incremental treadmill exercise test until exhaustion. Blood was taken before and 1 hour after the test. In part II of the study 8 healthy volunteers performed an anaerobic training for 5 days consisting of 4 × 400 m runs per day (2 in the morning; 2 in the afternoon). Blood was taken at day 1 before training and the day after the last training unit. Lymphocytes were isolated using density-gradient centrifugation. Intracellular pH was measured using the pH sensitive fluorescent indicator BCECF. Cells were acidified using propionic acid and the pHi recovery was investigated. Mean resting pHi of lymphocytes isolated before exercise was 7,26 ± 0,01. Exercise did not affect resting pHi. In contrast, the recovery of pH after acidification of lymphocytes was significantly enhanced after both the treadmill test and the 5 day anaerobic training. These results indicate that acid-loading during anaerobic exercise increases Na+-H+-exchanger activity in human lymphocytes. Moreover, a single bout of exercise is sufficient to induce an exchanger adaptation and after anaerobic training this adaptation lasts for at least 24 hours after the last training unit.

THE ACUTE EFFECTS OF EXHAUSTIVE EXERCISE ON SERUM IMMUNOGLOBULIN IN ASYMPTOMATIC HEPATITIS B CARRIERS

Viral hepatitis is a common infection worldwide. However, few studies have focused on the relationship between exercise and immune function in patients with hepatitis. The purpose of this study was to examine the serum immunoglobulin response to exhaustive exercise in asymptomatic hepatitis B carriers. The study included: nine subjects (20.9íÓ1.6yrs) who were asymptomatic hepatitis B carriers (AHB); and nine healthy subjects (21.3íÓ1.0yrs) who served as the control group (CG). All subjects performed an incremental treadmill exercise test to exhaustion. Blood samples were collected pre-exercise (Pre), and at 5 min, 3h, 24h and 48h post-exercise. Serum IgM, IgG and IgA were analyzed. There were no significant differences between the AHB group and the CG group in immune response to exercise. Also, serum IgM, IgG and IgA in different time points were not significantly different after exercise. Although there were no significant differences, there was a trend towards lower IgA and IgG from 3h to 48h in both groups. After exercise, the lowest Ig values occurred earlier in the AHB group (at 3h) than the CG (at 24h). The results of this study suggest that in individuals with asymptomatic hepatitis B, serum IgM, IgG and IgA will not be affected by acute maximal exercise. However, the open window of immunosuppression may be different between patients with asymptomatic hepatitis B and healthy individuals. Further study is needed to identify the exact difference.

Chronic fatigue syndrome: is it physical?

It is increasingly recognized that chronic fatigue syndrome (CFS) is heterogeneous. A significant proportion of patients fulfilling operative criteria for a diagnosis of CFS will also fulfill criteria for a psychiatric disorder, such as depression or somatization. Failure to recognize this heterogeneity prejudices attempts to understand CFS in cross-sectional studies. Fulcher and White recently reported a study of muscle strength, aerobic exercise capacity, and functional incapacity in a group of patients with CFS without concurrent psychiatric disorder, compared with patients with major depression and a group of normal but sedentary subjects.1 In an incremental treadmill exercise test, patients with CFS and patients with depression had lower peak oxygen consumption rates, maximal heart rates, and plasma lactate concentrations than the sedentary controls; but this reflected the shorter duration of exercise tolerated by these patients. At submaximal work rates, patients with CFS and depressed patients experienced greater perception of effort than sedentary controls at the same level of work. This is in keeping with the finding that such patients show greater sensitivity to bodily sensations than normal subjects. Overall, there was little difference between the patients with CFS and the depressed patients in exercise characteristics, yet the patients with CFS reported significantly greater physical fatigue and physical incapacity. The authors did find one important difference, however. Their patients with CFS were significantly weaker than either the depressed patients or the sedentary controls, as judged by measurement of quadriceps strength. This is the first study to demonstrate such physical weakness in patients with CFS, and the authors suggest that this is because the patients they studied were more coherent than those studied previously. Fatigue is a complex symptom. In its strictest sense, the word means “inability to sustain force,” indicating dysfunction in the neuraxis or neuromuscular apparatus, whether physiologic (after strenuous exercise) or due to disease processes. In its colloquial context (fatigare—to tire), it is the sensation experienced when the effort to perform work, whether physical, mental, or both, seems disproportionate for the task involved. Physiologic fatigue recovers with rest. Chronic fatigue typically does not. Although chronic fatigue is a common complication of a wide range of medical and neurologic diseases, such as multiple sclerosis and Parkinson's disease, it can also occur in the absence of readily definable disease, notably in CFS. What is the cause of this physical weakness in CFS? Fulcher and White think that it is related to physical deconditioning due to inactivity, and this view is supported by improvement in well-being, strength, and exercise capacity after a graded aerobic exercise program.2 However, graded exercise therapy improves tolerance and exercise capacity in many disorders, including muscle diseases such as mitochondrial myopathies.3 Some patients with CFS show abnormal increases in plasma lactate levels after exercise at low work rates.4 Heart rate responses to exercise in the 1995 study did not suggest that these patients with CFS were more “deconditioned” than those with normal lactate responses. They also proved less likely to have psychiatric disorder. Furthermore, recent spectroscopic studies of the forearm muscles, which are not usually subject to the effects of deconditioning, showed abnormal muscle energy metabolism in such cases.5 Deconditioning may well be an important factor in the pathogenesis of CFS, but these findings raise the possibility that some patients with CFS have a form of metabolic myopathy. Whatever the mechanisms underlying “fatigue,” exercise therapy is likely to become an increasingly important therapeutic modality in various fields and particularly in the management of chronic fatigue syndromes.

Peak aerobic performance and left ventricular morphological characteristics in university students.

To determine whether a relationship exists between left ventricular morphology and aerobic capacity in large numbers of male university students with a physically inactive and active life style. A prospective study. Sports medicine research center. Eleven sedentary normal-weight university students, 17 sedentary overweight university students, and 215 university athletes. After the echocardiographic examination, an incremental treadmill exercise test until exhaustion was performed to measure peak oxygen uptake (VO2). In sedentary students, absolute peak VO2 in the overweight students was slightly higher than that in normal-weight students (3,024 vs. 2.912 ml/min). Relative peak VO2 (ml/min/kg) was highly negatively correlated with body mass index (kg/m2) in a total of 28 sedentary students. The correlation between absolute peak VO2 and left ventricular dimension was weak in the sedentary overweight students; however, a correlation coefficient of 0.55 was obtained in athletic students. A stepwise multiple regression showed significant determinants of absolute peak VO2 in athletic students for body surface area (45%), left ventricular dimension (7%), and certain sports (6%). A physically active life style plays a role in increasing both aerobic capacity and left ventricular enlargement. Body size appeared to be a potent stimulus to left ventricular enlargement.

Exercise endpoints in patients with chronic heart failure

Background: Peak oxygen consumption ( V̇ O 2 ) is a powerful predictor of outcome in patients with chronic heart failure. This is not a test that is readily clinically available. We therefore sought to establish a method of assessing peak V̇ O 2 from non-invasively acquired data. Methods: We analysed the results from incremental treadmill exercise tests in 60 patients [aged 59.0 (S.D. 12.4) years] with chronic heart failure or left ventricular dysfunction [left ventricular ejection fraction (29.6 (15.2)%)] and 52 control subjects [aged 36.7 (12.3)]. Metabolic gas exchange during exercise was measured with a respiratory mass spectrometer. Heart rate and blood pressure were measured. Results: Peak V̇ O 2 was lower in patients than controls [19.9 (7.7) ml/kg/min vs. 38.3 (9.0), P<0.001]. Exercise time ( r=0.84, P<0.001), heart rate at peak exercise ( r=0.63, P<0.0001), change in heart rate ( r=0.72, P<0.0001), rate pressure product at peak exercise ( r=0.64, P<0.0001) and change in systolic blood pressure ( r=0.31, P=0.002) all correlated with peak V̇ O 2 . In a stepwise regression model, exercise time was the most powerful predictor of peak V̇ O 2 ( r 2=0.79). The only additional independent variable was change in heart rate from rest to peak exercise, which increased r 2 to 0.80. In a survival analysis, measured peak V̇ O 2 and the peak V̇ O 2 estimated from exercise time and change in heart rate had similar predictive power. Conclusions: In this preliminary study, peak V̇ O 2 can be estimated from non-invasively acquired parameters. Estimated peak V̇ O 2 and measured peak V̇ O 2 have similar predictive power for outcome. Further work is necessary to see if estimated peak V̇ O 2 is widely applicable in a clinical setting.

Effect of intravenous administration of furosemide on mass-specific maximal oxygen consumption and breathing mechanics in exercising horses

Abstract Objectives To determine whether IV administration of furosemide (250 mg) to horses before maximal exercise affected maximal oxygen consumption (V⃙o2max), breathing mechanics, or gas exchange during exercise. Animals 7 healthy, well-conditioned Thoroughbred horses. Procedures 5 horses initially performed an incremental treadmill exercise test to determine V⃙o2max 4 hours after IV administration of furosemide (250 mg IV) or placebo (saline [0.9% NaCl] solution). Time to fatigue and distance run were recorded. All 7 horses were then used to determine the effects of furosemide on gas exchange and breathing mechanics at 40, 60, 80, and 100% of V⃙o2max. Horses were weighed immediately before exercise. Results Furosemide treatment significantly increased mass-specific V⃙o2max (5.3%), but absolute V⃙o2max was not significantly altered. In the 2 parts of the study, body weights were 2.9 and 2.5% higher when horses were given placebo than when they were given furosemide. Time and distance run at speeds ≥ 11.0 m/s were significantly greater following furosemide administration. Furosemide treatment had no effect on breathing mechanics or gas exchange. Conclusions and Clinical Relevance Previous studies have suggested that prerace administration of furosemide may have a positive effect on performance. Results of this study indicate that this may be attributable, in part, to an increase in mass-specific V⃙o2max but not to improvements in breathing mechanics or gas exchange. Most of the increase in mass-specific V⃙o2max appeared to be attributable to weight loss associated with diuresis induced by furosemide. (Am J Vet Res 1999;60:1415–1422)

Effects of phlebotomy and autologous blood transfusion on oxygen transport in the racehorse.

Because the haemoglobin concentration Hb[ during exercise may be at the upper limit of blood viscosity for effective oxygen delivery, we hypothesised that administration of blood would not further enhance oxygen delivery or exercise capacity. Six Thoroughbred geldings were used in 5 incremental treadmill exercise tests over a period of 4 weeks. The first test was performed 6 days prior to phlebotomy, which involved the removal of 20 ml/kg bwt of venous blood. Exercise tests were performed at 1, 8 and 15 days after blood removal. Six days after the 15 day post phlebotomy exercise test, blood from each horse was reinfused and the final test performed 24 h after blood reinfusion. During the 3 weeks following blood collection, the blood, collected into acid citrate dextrose, was stored at 3 degrees C. Each exercise test involved measurements of arterial and mixed venous blood gases, plasma lactate concentrations, heart rate and VO2 using an open flow system. Cardiac output was measured by direct Fick. The removal and reinfusion of blood had significant effects on packed cell volume (PCV) with the lowest PCV value during exercise of 0.57 +/- 0.04 l/l being recorded in the second post phlebotomy test and the highest value of 0.67 +/- 0.04 l/l found after blood reinfusion. There were no significant effects of phlebotomy or blood reinfusion on arterial blood gas values. However, arteriovenous oxygen content difference was significantly altered by phlebotomy and reinfusion. The maximal values during the 3 tests following phlebotomy were significantly lower (P < 0.05) by about 7% than those before phlebotomy and after blood reinfusion, mirroring the alterations in Hb[. There was no significant effect of phlebotomy or blood reinfusion on heart rate but stroke volume was significantly higher (P < 0.01) during the 3 post phlebotomy tests than for the control or blood reinfusion tests. There was no significant effect of phlebotomy or blood reinfusion on either the submaximal or maximal values for VO2. No significant effect of blood removal or reinfusion was found on the treadmill run time to fatigue. We concluded that haemodynamic adjustments following phlebotomy or blood reinfusion maintained oxygen delivery during exercise. No detrimental effects on exercise capacity were found from phlebotomy nor beneficial effects from autologous blood transfusion. However, it should be noted that the extent of change induced in Hb[ was relatively small and with the number of horses in the study, the experimental power was not great.

Effect of breathing frequency and airflow on pulmonary function in high-intensity equine exercise.

It has been postulated that the hypoxaemia and hypercapnoea that characterize strenuous equine exercise are partly due to flow limitations imposed by high breathing frequencies (fb), and that gas exchange would be improved if fb could be lowered. To evaluate this possibility, 6 Thoroughbred horses underwent 4 incremental treadmill exercise tests at inclines of 0, 5, 10 and 25%, respectively. In the test, horses were given a warm-up for 2 min, then ran sequentially for 1 min each at 60, 100 and 115% VO2max. Oxygen consumption (VO2), blood gas tensions (PaO2, PaCO2), fb, tidal volume (VT), minute ventilation (Ve), transpulmonary pressure (Ptp), peak inspiratory and expiratory airflows (VI, VE) and work of breathing (Wrm) were determined during the last 15 s of exercise at each intensity. The only effect of fb on PaO2 was seen at 60% VO2max. Also, maximal transpulmonary pressure difference (delta Ptpmax), and peak VI, and VE on a 25% slope were lower than those recorded at the other 3 inclines at 60% VO2max. At 100 and 115% VO2max, the effect of fb was less clear. While fb still differed, the only effects of fb at 100% VO2max were on delta Ptpmax. At 115% VO2max, fb on a 25% incline was lower than that for 0 and 5% slopes. The only other difference noted at this intensity was in VT on 10% slope. However, there was no difference between VTS recorded at inclines of 0, 5 or 25% at 115% VO2max. There was no effect of fb or exercise intensity on Ve at 100 or 115% VO2max. There was no change in PaO2, fb, VT, delta Ptpmax or VI and VE as exercise intensity increased from 60-115% VO2max on slopes of 0, 5 or 10%. However, for exercise on the 25% incline (i.e. with lower fb), each of these parameters increased (or decreased for PaO2) from 60-100%, but not from 100-115% VO2max. Failure of peak airflow and VT to increase when intensity increased was associated with the development of hypoxaemia and hypercapnoea, regardless of slope or fb. It is concluded that while a low fb may have some beneficial effect on gas exchange during submaximal exercise at approximately 60% VO2max, this effect disappears as exercise intensity increases. There appear to be limits to the peak airflows that can be generated by horses during strenuous exercise, and these limits may be reached regardless of fb. Flow limitation per se may play a greater role in the development of exercise-induced hypoxaemia and hypercapnoea in horses than dose fb.

Effect of feeding thoroughbred horses a high unsaturated or saturated vegetable oil supplemented diet for 6 months following a 10 month fat acclimation.

This study looked at the effect of feeding diets supplemented with either a predominantly saturated or unsaturated vegetable oil over a prolonged period to exercising horses. Eight Thoroughbred horses were assigned to 2 diet treatments and for 10 months were fed Timothy hay and oats, together with a fortified sweet feed supplemented with either a predominantly unsaturated (Un) or a saturated (S) vegetable oil so that approximately 19% DE (Digestible Energy) came from dietary fat and approximately 12% from either the Un or S source (AC). An increased amount of Un or S fortified sweet feed, replacing the oats, was then fed for a further 6 months (HF) so that approximately 27% DE came from fat and approximately 20% from the Un or S vegetable oil. Standardised incremental treadmill exercise (8-12 m/s) tests (STEP) and duplicate oral glucose tolerance tests (TOL) were carried out after 3, 6 and 9 months of the AC diet and after 3 and 6 months on the HF diet. There was no significant effect of dietary treatment or when the tests were undertaken (time) on the insulin or lactate responses to the STEP tests. Overall there was a significant (P < 0.05) effect of time and treatment on the glucose response, but there was no difference between treatments at the first and last tests or between the results for these tests or between the endAC and endHF tests. No significant effect of treatment or time was seen on the TOL glucose response (% change from Time '0') although there was a trend for the glucose concentrations to be lower and the insulin responses higher (nonsignificant) in the S treatment group. No significant effect of treatment on haematological parameters, monitored monthly, was found. Total protein and gamma glutamyl transferase remained within the normal range throughout. There was a significant effect of treatment (P < 0.05) on cholesterol and triglycerides with higher concentrations in the S group from the first (1 month) sample. Linoleic acid was the main fatty acid in all the 4 plasma lipid classes with slightly, but significant (P < 0.05), higher concentrations in Un for the cholesterol ester and phospholipid classes. There was no effect of time. Overall, the total resting plasma fatty acid content was significantly higher (P < 0.05) with S at the sample points (endAC and endHF). No adverse effects of feeding either diet on apparent coat condition or hoof appearance were seen apart from an apparent increase in the grease score. Many of the parameters assessed showed significant improvements with time (P < 0.05). In conclusion, no apparent adverse effects of feeding a diet supplemented with either an unsaturated or saturated vegetable oil for 6 months at approximately 20% DE after 10 months at approximately 12% DE were identified and there were no apparent disadvantages of feeding a saturated vegetable oil supplemented diet compared with an unsaturated one.

Muscle anaerobic response to a maximal treadmill exercise test in Standardbred trotters.

The purpose of this study was to develop a standardised maximal treadmill exercise test performed until fatigue in order to find reproducible markers for anaerobic metabolism, specifically adenine nucleotide degradation. Six Standardbred trotters performed an incremental maximal treadmill exercise test in 1 min steps (starting with 7 m/s) until they could no longer keep pace with the treadmill. The test was performed twice with at least one week between the tests. Heart rate was recorded and venous blood samples were obtained during the test and in the recovery period for determination of plasma lactate, hypoxanthine, xanthine and uric acid. Muscle biopsy samples (m. gluteus) were collected at rest, immediately post exercise, and after 15 min recovery and analysed for their concentrations of glycogen, creatine phosphate (CP), adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), inosine monophosphate (IMP) and muscle lactate (MLa). Significant decreases in glycogen, CP and ATP and significant increases in IMP and MLa were seen immediately post exercise. None of these metabolites had returned to resting levels after 15 min of recovery. A marked increase in plasma lactate (PLa) occurred during exercise and the peak concentration (mean value = 27.2 mmol/l) was reached within 5 min of recovery. Plasma uric acid concentration did not increase during exercise but rose markedly immediately post exercise, reaching the highest level (mean value = 121.5 micromol/l) at 20-30 min recovery. The duration of the maximal test was related to peak PLa and the uric acid concentration at 30 min of recovery. A correlation was also found between the ATP and IMP concentrations immediately post exercise and the plasma uric acid concentration at 30 min of recovery. The results show that this treadmill test triggered anaerobic metabolism and also that uric acid concentration post exercise seems to be a marker for the adenine nucleotide degradation that occurs during intense exercise. No significant differences were seen in metabolic response between the 2 test occasions.

Effect of nasal occlusion on tracheal and pharyngeal pressures in horses

Abstract Objective To compare tracheal and pharyngeal inspiratory and expiratory pressures achieved during 60 seconds of nasal occlusion in standing horses with pressures achieved in horses during intense exercise. Animals 5 Standardbreds. Procedure Tracheal and pharyngeal inspiratory and expiratory pressures were obtained from 5 horses during 60 seconds of nasal occlusion and compared with tracheal and pharyngeal pressures achieved during incremental treadmill exercise tests in which horses ran at 50, 75, and 100% of the speed that resulted in maximal heart rate ( HRmax) Results Significant difference was not detected between peak tracheal inspiratory pressure during nasal occlusion and peak tracheal inspiratory pressure at HRmax. Peak pharyngeal inspiratory pressure was sig nificantly more negative, and peak tracheal and peak pharyngeal expiratory pressures were sig nificantly more positive during 60 seconds of nasal occlusion than those observed in horses running at HRmax. Conclusion During upper airway endoscopy in standing horses, 60-second nasal occlusion induced tracheal and pharyngeal inspiratory pressures that equaled or exceeded pressures achieved during high-intensity exercise. Clinical Relevance Nasal occlusion is useful to simulate upper airway pressures achieved during high-intensity exercise. (Am J Vet Res 1996;57:1258–1260)

CARDIORESPIRATORY RESPONSES TO EXERCISE AFTER THE VENOUS SWITCH OPERATION FOR TRANSPORTATION OF THE GREAT ARTERIES 236

The effect of a 3.4 year time period on the exercise performance of 16 children following surgical repair for transposition of the great arteries(TGA) was evaluated. Children ranged in age from 5 to 18 with a mean age of 8 years. Incremental treadmill exercise testing was performed prior to and following this time period to track whether the cardiorespiratory response to exercise would be altered during normal growth following surgery for complex congenital heart disease. The data collected at both measuring sessions was compared to that of 234 age matched healthy children (C). Subjects with TGA had significantly lower values for (VT) (76% of normal), peak VO2 (85% of normal) and a significantly higher peak VE/VO2 (112% of normal) at the first measuring session. These parameters remained significantly below normal but stable in the TGA subjects following the 3.4 year time period. We conclude that exercise cardiac function of children with surgically corrected TGA is diminished compared with control children and that rehabilitation is needed to improve their cardiorespiratory response to exercise.

Physiological versus clinical consequences of left recurrent laryngeal neuropathy (LRLN)

SummaryThe clinical implications of ventilatory alterations induced by left recurrent laryngeal neuropathy (LRLN) are reduced performance due to increased metabolic requirements for breathing and a reduction in peak aerobic power (V̇O2peak). To test this hypothesis, the metabolic cost of locomotion (MCL) and peak aerobic power (V̇O2peak) were measured in 4 non racing crossbred horses (low V̇O2peak) with reversibly induced LRLN using an incremental treadmill exercise test. Reversible LRLN was achieved with regional anaesthesia. These results were compared to previous measurements in 4 Thoroughbred racehorses (high V̇O2peak, Ehrlichet al.1993). No significant difference in MCL (based on V̇O2and venous lactate) was found in either group of horses at exercise intensities where V̇O2&lt; V̇O2peak(&lt;9 m/s). Peak aerobic power decreased by 15.3% (140.0 ± 3.2 vs. 165.3 ± 3.4 ml/kg/min ± s.e., in the Thoroughbred racehorses (high V̇O2peak) with induced LRLN but not in the non racing horses with lower V̇O2peak(135.0 ± 4.5 ml/kg/min ± s.e. The results of these 2 studies indicate that alterations in ventilation due to LRLN cause a significant reduction in V̇O2peakonly in horses with high V̇O2peak. At exercise intensities where V̇O2&lt; V̇O2peak, MCL was not increased in either group of horses despite ventilatory alterations induced by LRLN.

Effect of gas collection system on respiratory and stride frequency and stride length

SummaryThe objective of this study was to determine the effects of 2 different gas collection systems on locomotor and ventilatory responses to exercise in a group of 8 Standardbred pacers. Each horse completed the same incremental treadmill exercise test (8, 9, 10 and 11 m/s on a 3° incline) using an open (flow‐through) system (OS) and a closed system (CS) incorporating one way valves. Only 2 horses completed the final (11 m/s) step using the CS. Peak values for V̇O2, O2 pulse, plasma lactate and respiratory exchange ratio (RER) were significantly higher for the OS compared with the CS. There was no change in breathing frequency (Vf) or stride frequency (Sf) (mean ± s.e. 128 ± 2 strides/min) throughout either exercise test, however Vf was significantly lower when horses exercised in the CS (68 ± 6 breaths/min) when compared to the OS (100 ± 3 breaths/min). There was a linear increase in stride length (SL) with speed (3.8 ± 0.1 m/stride at 8 m/s to 5.0 ± 0.2 m at 11 m/s) but no difference in SL between systems. There was also a linear increase in VT measured in the CS. Incremental exercise did not alter the Sf:Vf ratio, however Sf:Vf was significantly lower in the OS (1.3:1) when compared to the CS (2.1:1). There was a significant difference between systems for PaO2 and PaCO2 values at all increments of exercise. The lower Vf measured in the CS was associated with marked hypercapnia (59 ± 7 mmHg at 10 m/s) and hypoxaemia (45 ± 3 mmHg at 10 m/s). The higher Vf measured in the OS was associated with hypocapnia (35 ± 2 mmHg) at 8 m/s. It was concluded that although Vf varied between OS and CS, Vf and Sf did not change during incremental exercise with either system. Therefore the increase in speed was achieved solely by an increase in SL. Although the CS did not alter locomotor parameters or V̇O2 at lower increments of exercise, the altered Vf appeared to limit work capacity.

Effect of a diet containing supplementary fat on the capacity for high intensity exercise

SummaryThis study investigated the effects of increased fat consumption on aerobic and anaerobic performance. Eight Thoroughbred horses that had undergone a 9 week, 6 days/week conditioning programme were randomly divided into 2 groups,Group F(5 horses) andGroup C(3 horses). For 2 weeks before the study all horses consumed a standard diet (2% fat) fed as 2 equal portions. Horses then undertook an incremental treadmill exercise test (+10% slope); 3 min at 4 m/s, 2 min at 6 m/s and 1 min at 8 m/s. Speed was then increased by 1 m/s every 60 s until fatigue. Maximal accumulated oxygen deficit (MAOD) was determined 72 h later. Horses inGroup Fwere then fed a diet containing 12% of the digestible energy in the form of fat (390 ml corn oil), a diet that was isocaloric with the control diet. Horses inGroup Ccontinued to receive the standard diet. All horses continued training (3600 m/day, at speeds up to 10 m/s, 6 days/week). After 4 weeks, the exercise tests were repeated. Prior to fat supplementation, V̄O2maxwas mean ± s.e. 145 ± 5.3 and 148.0 ± 6.0 ml/kg/min, time to fatigue during the MAOD test was mean ± s.e. 84.2 ± 18.4 and 85.0 ± 14.8 s, mean ± s.e. peak plasma [lactate] was 24.8 ± 3.1 and 23.5 ± 1.7 5 mmol/l and MAOD was 56.5 ± 5.3 and 68.1 ± 4.7 mlO2eq/kg forGroups FandCrespectively. The V̄O2maxand run time to fatigue in the incremental exercise test did not change in either group following fat supplementation. Run time (mean ± s.e. 97.2 ± 17.8 s), MAOD (65.5 ± 6.2 mlO2eq/kg) and peak plasma [lactate] (29.5 ± 2.6 mmol/l) increased during the MAOD test inGroup Fbut remained unchanged inGroup C.Resting muscle [glycogen] depletion during the MAOD test was not altered by the dietary manipulation. Provision of an increased proportion of the diet in the form of fat increased high intensity exercise capacity and the MAOD during intense treadmill exercise.